Conventionally, by switching the switch of each device using a network management system (NMS) according to a manual operation of an operator in each layer, an end-to-end path is set, and an alarm mask for each path is controlled.
Recently however, a time required to make a path setting can be shortened by a setting from a network management system, a route calculation in each device, and a path setting by signaling. For example, a route calculation is performed in a device using a signaling protocol (RSVP (resource reservation protocol) such as an MPLS (multi-protocol label switching), a GMPLS (generalized multi-protocol label switching), etc., RSVP-TE (resource reservation protocol-traffic engineering) etc., a routing protocol (OSPF (open shortest path first), OSPF-TE (open shortest path first for traffic engineering), etc.). On the basis of the route calculation, the devices included in the route of a path communicate signaling messages among them, thereby checking and implementing a system for setting a path.
On the other hand, the path control after making a path setting is still performed by manual switching for each layer by an operator. The path control is mostly required when a device is transferred due to trouble or is tested in the course of implementing optical fiber, replacing a package, etc. To control an alarm mask etc. of a path, a network management system first checks the accommodation relationship among layers, and then each of the checked paths is to be controlled. However, since there are a large number of lower-level paths accommodated in a higher-level path, a long time is taken to control the paths, and undesired alarms are frequently raised. For example, since a path OC-192 can accommodate 192 paths STS-1, the lower-level paths are to be controlled 192 times for each path OC-192. Furthermore, when 100 wavelengths are multiplexed on one optical fiber using wavelength division multiplexing (WDM), nearly 20 thousands of paths may be controlled.
Although performing path control on a number of paths is laborious work, a fault notification cannot be issued when a fault occurs if control is preliminarily performed by alarm mask etc. on all higher-level paths and lower-level paths in older to take into account a transfer due to trouble and a test.
FIG. 1 is an example of the state in which a fault occurs after an alarm mask is applied in advance to all higher-level paths and lower-level paths. An electric path 1 is set between two synchronous digital hierarchical (SDH) cross-connect devices 101a and 101b illustrated in FIG. 1, and an optical path 2 is set between cross-connect devices 102a and 102c. The electric path 1 is accommodated in the optical path 2.
(1) An operator 3 performs alarm suppression on the optical path 2 with respect to the WDM cross-connect device 102a (3a in FIG. 1). Then, a signaling message 40 in which an alarm suppression bit 31 is set to alarm suppression (A=1) passes through the optical path 2. By the signaling message 40, an alarm for the optical path 2 is suppressed in each of the WDM cross-connect devices 102 (102a, 102b, and 102c).(2) When the operator 3 performs the alarm suppression on the electric path 1 with respect to the SDH cross-connect device 101a (3b in FIG. 1), the signaling message 30 in which the alarm suppression bit 31 is set to alarm suppression (A=1) passes through the electric path 1 as with the optical path 2. By the signaling message 30 passing through the electric path 1, an alarm on the electric path 1 is suppressed in the SDH cross-connect devices 101 (101a and 101b). The operator 3 controls the alarm suppression on each of the 192 electric paths 1 accommodated in optical path 2.(3) When the alarm suppression is set on all WDM cross-connect devices 102 and SDH cross-connect devices 101 (A=1), any of the devices does not raise an alarm although a fault occurs between the devices 102c and 101b, thereby failing in detecting the fault.
As a related art of the method for removing an unnecessary alarm, Japanese Laid-open Patent Publication No. 11-252049 discloses the method for removing an unnecessary alarm by changing the number of multiplexed wavelengths when a fault, e.g., optical input disconnection, occurs in an optical fiber.